Pathologic conditions, primarily obstruction, result in changes in ureteral length and diameter, which in turn affects the ability of the ureter to contract. Abnormalities in ureteral function may in turn lead to deterioration of renal structure and function. In addition, preliminary data have suggested that there are age dependent changes in the ureter that in themselves effect its function and that influence its response to obstruction. As an example, it is apparent clinically that obstruction results in more extensive ureteral dilatation in the neonate than in the adult. Furthermore, our preliminary data have suggested that the neonatal rabbit ureter undergoes greater dimensional deformation in response to obstruction, has a different sensitivity to neurohumoral agents, i.e. catecholamines, and has a higher level of endogenous cyclic adenosine 3',5'-monophosphate (cAMP) than does the adult ureter. Thus there are apparent differences in the structure and pharmacologic responses of the neonatal and adult ureter which affect their ability to function. The full extent of and reason for these age dependent variations in ureteral mechanical and pharmacological properties is not known. It is planned to define the age related changes in the mechanical properties and pharmacologic responses of the neonatal, adult, and elderly adult ureter. The effects of age on the interrelationships of intraluminal pressure, wall tension, length and diametral deformation, and the force velocity of contraction will be determined. In addition, changes in the pharmacologic properties, i.e. response to neurohumoral agents, catecholamine content, endogenous cAMP levels and adenylase cyclase and phosphodiesterase activity, as affected by aging and disease will be investigated. It is hoped that this information concerning ureteral smooth muscle may give insight into methods of management of the ureter in pathologic conditions.